Hsu, U.S. Pat. No. 6,310,417, issued Oct. 30, 2001, disclosed an electric machine with uncluttered rotor magnetic coupling that has a significant potential to lower the cost of adjustable-speed drives. In addition to speed control below synchronous speed, this machine may also be operated above synchronous speed.
The term “uncluttered coupling” relates to a stator and rotor that couple slip energy. In an induction motor, the speed of the rotating stator field equals the sum of 1) the speed of the rotating rotor field plus 2) the mechanical rotation speed of the rotor. With the motor running at maximum torque and close to synchronous speed, rotor speed is high and slip (the difference between the speed of the rotating stator field and the rotational speed of the rotor) is small, about 3 to 10 per cent, and the slip frequency induced in the rotor is small, perhaps two to six cycles per second for a 60 Hz motor.
To couple only slip energy, the stator and rotor have coils that run circumferentially, sometimes referred to as “peripherally,” around the axis of rotor rotation. The peripheral coils of the rotor and stator are magnetically coupled. The rotor coil rotates and carries a slip-frequency current. Because the rotation does not change the total magnetic flux linking both the rotor and stator coils, no electromotive force (emf) is induced in the stator coil due to the rotation of the rotor coil. This “uncluttered coupling” allows only the slip energy power corresponding to the slip-frequency currents to be transferred between the rotor and stator coils of the transformer.
Hsu, U.S. Pat. Appl. Ser. No. 10/706,577, filed Nov. 12, 2003, disclosed an uncluttered machine with an additional PM rotor carrying permanent magnet material. This machine is capable of setting up torques and counter torques due to the reaction of the uncluttered rotor to the PM rotor.
It is desired to make such a machine that is applicable to the hybrid motor vehicle that uses both an electric machine and an internal combustion engine.